Best to Test Water-Heater Valve Twice a Year

Question: Our water heater’s safety pressure valve runs all the time and drains water out of the tank. Why?

Answer: Water heaters have a temperature-and pressure-relief valve designed to prevent the heater from exploding.

Some manufacturers suggest testing the valve every six months or so by raising and lowering its test lever. This should produce a sudden burst of hot water from the drain line connected to the valve. More frequent testing can reduce the chance of a leak caused by mineral and corrosion buildup.

If a leak occurs immediately after a test, operate the test lever several times to free lodged debris that might be preventing the valve from seating properly.

There are a few reasons why your valve runs all the time, wasting water and energy. Corrosion might have built up on the valve. Try flipping the test lever up and down a couple of times and tapping the stem with a hammer to seat the valve. If this doesn’t do the trick, make sure that the thermostat (on the controller) hasn’t been turned up. It should be set on medium for the safest and most efficient operation.

Excessively hot water will cause the pressure and temperature relief valve to open: It’s doing its job. Test the temperature of the water by using a thermometer in a glass filled with hot water from the tap. The temperature should not exceed 130 degrees.

Finally, excessively high water pressure can cause the temperature and pressure relief valve to leak. Residential water pressure should run between 30 and 55 pounds per square inch. Greater pressure can damage washing machines, dishwashers, ice makers and other water-supplied appliances.

Most homes have a water-pressure regulator valve where the water enters the building.

You can test the water pressure by using a gauge available from the hardware store. Screw the gauge onto a hose bib and turn on the water.

You can adjust the water pressure by turning a nut or screw on the pressure regulator.